28 Feb
2016
28 Feb
'16
8:53 p.m.
On Sun, 28 Feb 2016 20:27:34 +0100
Raphaël Mouneyres <rmouneyres(a)gmail.com> wrote:
What speed does a standard USB keyboard encoder work at?
Can it's clock be sped up without upsetting the USBlink?
Although speed wasn't an issue for me, I once used an old keyboard for this (had
intermittent key contacts) and just wired a discrete switch matrix onto it, for
dedicated functions.
--
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.
Such a
software would have to vary according to the keyboard model, the
available GPIO ports and the extra electronic components used (e.g.
shift registers or de-multiplexers).
Most keyboards are arranged in a matrix fashion so they have about 16 wires for a 64
notes keyboard.
this may already bee too much for a raspberry, so using a multiplexer is probably
mandatory.
A general purpose operating system like Linux is
not best suited for
such an application, since the scanning rate should be in the
sub-millisecond range to get a good velocity resolution (assuming you
have a keyboard with two contacts per key).
A project that generally does what you want is midibox.
Yes, i have built several midiboxes and also arduino alikes, so very familiar with this
easy and efficient way to do midi thing.
I mentioned I would like to avoid extra boards and use ressources existing on the cpu
board.
A few multiplexer chips are still easier/cheaper than any midiboard.
As you say, the sub-millisecond timing for the keyboard scanning is important, so if it
is not doable in-the-box, even with some real-time kernel and associated module, i would
certainly go with those solutions.
Raphaël